Voltage compensating circuit for X-ray apparatus



Sept- 1, 19 4 c. FLEGEL ETAL VOLTAGE COMPENSATING CIRCUIT FOR X-RAY APPARATUS Filed Sept. 8, 1961 United States Patent 3,147,382 VGLTAGE CUMPENSATING CIRCUIT FOR X-RAY APPARATUS Curt Flegel, Hamburg, Volirstlorf, and Rudolf Lange, Hamburg, Germany, assignors to North American Philips Company, Inc, New York, N.Y., a corporation of Delaware Filed Sept. 8, 1961, Ser. No. 136,925 Claims priority, application Germany Oct. 10, 1960 6 Claims. (Cl. 250-403) The invention relates to a device for the compensation of voltage losses of apparatus, in particular to X-ray diagnostic apparatus with pre-adjustment of the voltage values. In such apparatus, the operating voltage of the tube should be accurately determined for determining the hardness of the X-rays. If the apparatus is constructed for operation with only one tube of a definite load characteristic, there is no ditficulty in stepping up the supply voltage to the desired high voltage for the X-ray tube while considering the voltage drops which occur, for example, in the supply, in the transformer and in the carbon rollers of the transformer.

It becomes more difiicult when the X-ray apparatus is to be operated with several X-ray tubes of different load characteristics. Since the voltage drop in the apparatus is a function of the tube power, which in turn depends on the exposure time, it becomes necessary to incorporate for each tube a separate compensation of the voltage drops matched to this power.

It is known to effect this compensation of the voltage drops at the supply side of the X-ray transformer, since the primary voltage is a measure of the high voltage. Therefore, in a known embodiment, resistors are provided on the supply side at the input to the transformer, which resistors are in a certain relation with the apparatus resistors connected at the output side of the transformer. As a result, for each tube, the voltage drop in the apparatus with respect to the no-load voltage is proportional to the tube power.

For a finer control of the compensation, it is known to provide the transformer on the primary side with tappings which are connected into circuit in accordance with the voltage drop. However, if a sufficiently fine compensation is to be obtained, and operation is to occur with a three-phase-transformer, the number of tappings increases so greatly that, in the case of a construction of the apparatus for three different tubes, they can no longer be housed in a normal switch board.

The object of the invention is to simplify the measures for the voltage compensation in that the change of the number of primary windings of the transformer, previously obtained by tappings, occurs through infinitely variable voltage control members, for example, carbon rollers.

According to the invention, a device is provided for changing the adjustment of the voltage control member in a manner such that the separate parts of the voltage loss, comprising a value dependent on the type of X-ray tube, and a voltage loss dependent on the exposure time, are converted into distances according to a logarithmic scale, and are then combined. According to a second logarithmic scale, this distance is converted into a variation of the adjustment of the voltage control member which is proportional to the total voltage loss.

The invention is based on the recognition that, on establishing the power of an X-ray tube as standard power and the voltage drop caused by this power, only a factor on need be added for all the other tubes, by which the power of the other tubes distinguishes from the standard tube. If the voltage drop of the tube with standard power which 3,147,382 Patented Sept. 1, 1964 is a function of the power and of the time and which satisfies the equation fu normj) is represented, in accordance with the load diagram of the standard tube as a function of the adjusted time, by the equation fnormu) it is sufiicient for the calculation of the voltage drop of any other tube to add the factor a to the equation of the standard tube:

This voltage drop can very simply be obtained by adding the logarithmitized multiplicand, in which the logarithmic sum of the total voltage drops results:

Log AU=log 04+ log f(t) The calculation of the sum is carried out by compounding distances on a stretched drawing member, for example, a rope, which is kept stretched by a drawing spring. By the elongation of the loop of the rope, which may occur by the extension of the loop by means of rollers, an apparent shortening of the original length of the rope is effected and consequently a shifting member provided on the rope is displaced. Since the elongation of the length of the rope within the loop of the rope occurs by means of rollers on a logarithmic scale, the displacement of the shifting member indicates the total voltage drop as a distance on a logarithmic scale.

The conversion of the logarithmic voltage drop distance into a natural distance occurs through a comparison drawing member which follows the displacements of the shifting member with a comparison member. On following, a logarithmic curved disc transmits the resulting logarithmic variation in length of a loop of the comparison drawing member through the shaft of the curved disc into a natural distance which is transmitted by voltage control members on the transformer.

This device can be extended at will and may take into account a voluntary number of other factors, in particular, by incorporating additional loops. Finally, the field of application of the device is not restricted to that of X-ray diagnostics. The device may also be used in those cases where the maximum number of transformer tappings are in use and a further increase is not feasible owing to a particularly fine distribution, and in which the tappings may be replaced by an infinitely variable current collector by the calculation of a product of the voltage variation factors to be considered.

In order that the invention may be readily carried into effect, one embodiment thereof will now be described, by way of example, with reference to the accompanying drawing.

In the device according to the invention a tube selector l is associated with each adaptation factor u of an X-ray tube, which is to be used in an X-ray diagnostic apparatus, not shown. All of the tube selectors 1 consist of pointer-shaped rods journalled on a shaft 3 and variable in their length by means of adjusting screws 4. If the apparatus is operated with a tube to be adapted, one of the tube selectors 1 presses on an arm 5 of a bellcrank lever '7 which is rotatable about its pivot 8 in accordance with a logarithmic scale. The tube selector 1 consequently determines the position of the free lever arm 9 on a logarithmic scale.

A second selection of the device occurs by means of a time selector It), on the shaft 11 of which a curved disc 12 is provided, the shape of which corresponds to that of a logarithmic spiral. In accordance with the direction of rotation of shaft 11, the curved disc 12 displaces the guide stud 13 of a shifting member 15 engaging the disc. Member 15 is moved in the direction indicated by the arrows, either away from the shaft 11 or towards the shaft 11.

A rope 21 is provided which links a roller 18 on the bell-crank lever 7 of the selector 1, a roller 19 on the shifting member 15 of the time selector 1t! and an additional roller 20 on the bell-crank lever 7. One end of the rope from the first roller 18, is fastened to the wall of the apparatus 22. After the last roller 28, the rope 21 is once again turned by a guide roller 23 and connected to a shifting member 24. The shifting member 24 is connected to a wall 22 of the apparatus via a draw spring 26, which keeps the rope stretched. Parallel to the first draw spring 26, a second draw spring 28 provided on the wall 22 of the apparatus keeps a comparison rope 30 stretched by means of a shifting member 29 connected to rope 30 and draw spring 28. As far as the guide roller 32, the rope 30 runs parallel to the rope 2i. Rope 3% is then turned about roller 32 and extends via roller 34 of a slide 36 to the wall 22 of the apparatus.

Two spring lever switches 38 are provided on the comparison member 29. The switches start a motor 39 either in counterclockwise rotation or in clockwise rotation at the instants at which the shifting member 24 is shifted owing to a different factor adjustment at the tube selector 1 or to a displacement of the curved disc 12 and an associated elongation or shortening of the rope loop 49. Switching on occurs by the shifting member 24 forcing down one of the switching levers 41 of the switch 38. The motor 39, after switching on, rotates a curved transmission disc 44 provided on the motor shaft 42, the circumference 45 of said disc having the shape of a logarithmic spiral. Via a stud 46 which presses on the circumference 45 of the curved transmission disc 44, the curved disc shifts the slide 36 and the rope roller 34 provided on it away from the motor shaft or allows it to approach this shaft. As a result, the loop 48 of the comparison rope 30 also increases or decreases between the roller 32 and the wall 22 of the apparatus, which results in a shifting of the comparison member 29 with respect to the shift ing member 24. The displacement stops when the comparison member 29 has followed the displacement of the shifting member 24 and the shifting member 24 allows the lever 41 which was pressed down to lift again. As a result of this, the motor 39 is switched off.

The motor shaft 42 at the same time actuates the driv ing belt 50 of a current collector carbon roller 52 which may be passed, for example, along the circumference of a ring transformer 54. In the device according to the invention, logarithmic rope lengths are added to the first rope 21 owing to a displacement of the rollers 18, 19, 20 on a logarithmic scale, which causes a variation of the length of rope within the rope loop 40. The logarithmic sum distance is indicated by the displacement of the shifting member 24. This logarithmic sum distance is measured with the comparison rope 30 which transmits the sum distance via the slide 36 to the logarithmic curved disc 44. The motor shaft 42 rotates and transmits the logarithmic distance plotted on the curved disc as a natural distance of the voltage drop to the transformer 54 by means of the carbon rollers 52.

What is claimed is:

1. Control apparatus for energizing a selected one of a plurality of electrical energy consuming devices comprising means for adjusting the supply voltage applied to said selected device, a first movable member arranged to move a distance which is a logarithmic function of a first variable quantity, said variable quantity being determined by the energy requirements of a selected one of said devices, a second movable member operable in response to the adjustment of the time of operation of said selected device, the movement of said second member varying as a logarithmic function of said time, means for combining the movements of said first and second members, means for varying the energy supplied to said selected device, and means for actuating said energy varying means comprising means for converting said logarithmic movements of said first and second members into a movement of a third member, said third member movement being logarithmically related to the movements of said first and second members.

2. X-ray control apparatus for energizing a selected one of a plurality of X-ray tubes comprising a first movable member arranged to move a distance which is a logarithmic function of a first variable quantity, said variable quantity being determined by the energy requirements of a selected one of said tubes, a second movable member operable in response to the adjustment of the time of operation of said selected tube, the movement of said second member varying as a logarithmic function of said time, means for combining the movements of said first and second members, said last mentioned means including a third movable member mounted for relative displacement and responsive to the movement of said first and second members, a comparison member operatively associated with said third member and disposed for relative displacement with respect to said third member, means for varying the energy supplied to said selected device, and means for actuating said energy varying means comprising means responsive to the relative displacement of said third member with respect to said comparison member for converting said logarithmic displacements of said first and second members into a displacement of a fourth member, said fourth member displacement being logarithmically related to said first and second displacements, said means for actuating being operatively connected to said comparison member whereby said comparison member is caused to follow the movement of said third member.

3. Apparatus according to claim 2 wherein said third member is mounted for linear displacement, said third member being displaced by an amount proportional to the logarithmic sum of the movements of said first and second members, and said comparison member being linearly displaceable in a direction parallel to said third member and by an amount equal to the displacement of said third member thereby to restore the apparatus to an equilibrium condition.

4. Apparatus according to claim 2 wherein said comparison member further comprises switching means actuated by the relative displacement of said third member with respect to said comparison member and said means for actuating further comprises a motor, said switching means controlling the energization and direction of rotation of said motor, said motor being the driving mechanism for the energy varying means and for said comparison member, said motor energization being controlled in a manner to cause said comparison member to realign itself with said third member to restore the apparatus to an equilibrium condition.

5. Apparatus according to claim 4 wherein said motor is operatively coupled to said comparison member by means of a flexible member maintained under tension.

6. Control apparatus for energizing a selected one of a plurality of X-ray tubes in an X-ray device comprising a voltage control member for adjusting the supply voltage applied to said X-ray device, a first rotatable member arranged to rotate through a distance which is a logarithmic function of a first variable quantity, said variable quantity being determined by the energy requirements of a selected one of said tubes, a second linearly displaceable member operable in response to the adjustment of the time of operation of said selected tube, the movement of said second member varying as a logarithmic function of said time, said first and second members being operatively linked by means of a flexible member maintained under tension, means jointly controlled by the movement of said first and second members, said last mentioned means including a third movable member mounted for relative displacement, and means for actuating said voltage control member comprising means responsive to the displacement of said third member for converting said logarithmic displacements of said first and second members into a movement of a fourth member, said fourth member movement being logarithmically related to the movements of said first and second members.

References Cited in the file of this patent UNITED STATES PATENTS 2,147,424 Bischoff Feb. 14, 1939 2,836,728 Maurice May 28, 1958 2,936,276 Hoekstra May 10, 1960 FOREIGN PATENTS 1,095,408 Germany Dec. 22, 1960 

2. X-RAY CONTROL APPARATUS FOR ENERGIZING A SELECTED ONE OF A PLURALITY OF X-RAY TUBES COMPRISING A FIRST MOVABLE MEMBER ARRANGED TO MOVE A DISTANCE WHICH IS A LOGARITHMIC FUNCTION OF A FIRST VARIABLE QUANTITY, SAID VARIABLE QUANTITY BEING DETERMINED BY THE ENERGY REQUIREMENTS OF A SELECTED ONE OF SAID TUBES, A SECOND MOVABLE MEMBER OPERABLE IN RESPONSE TO THE ADJUSTMENT OF THE TIME OF OPERATION OF SAID SELECTED TUBE, THE MOVEMENT OF SAID SECOND MEMBER VARYING AS A LOGARITHMIC FUNCTION OF SAID TIME, MEANS FOR COMBINING THE MOVEMENTS OF SAID FIRST AND SECOND MEMBERS, SAID LAST MENTIONED MEANS INCLUDING A THIRD MOVABLE MEMBER MOUNTED FOR RELATIVE DISPLACEMENT AND RESPONSIVE TO THE MOVEMENT OF SAID FIRST AND SECOND MEMBERS, A COMPARISON MEMBER OPERATIVELY ASSOCIATED WITH SAID THIRD MEMBER AND DISPOSED FOR RELATIVE DISPLACEMENT WITH RESPECT TO SAID THIRD MEMBER, MEANS FOR VARYING THE ENERGY SUPPLIED TO SAID SELECTED DEVICE, AND MEANS FOR ACTUATING SAID ENERGY VARYING MEANS COMPRISING MEANS RESPONSIVE TO THE RELATIVE DISPLACEMENT OF SAID THIRD MEMBER WITH RESPECT TO SAID COMPARISON MEMBER FOR CONVERTING SAID LOGARITHMIC DISPLACEMENTS OF SAID FIRST AND SECOND MEMBERS INTO A DISPLACEMENT OF A FOURTH MEMBER, SAID FOURTH MEMBER DISPLACEMENT BEING LOGARITHMICALLY RELATED TO SAID FIRST AND SECOND DISPLACEMENTS, SAID MEANS FOR ACTUATING BEING OPERATIVELY CONNECTED TO SAID COMPARISON MEMBER WHEREBY SAID COMPARISON MEMBER IS CAUSED TO FOLLOW THE MOVEMENT OF SAID THIRD MEMBER. 